With a semiconductor device pattern becoming finer, problems have occurred where a capacitance between wires increases due to a fringe effect generated between the wires and the reliability of the wires deteriorates due to a reduced distance between the wires.
As a measure to avoid the above increase in capacitance between the wires, it has been proposed to introduce an air gap between the wires.
In the conventional proposal, the air gap has been formed as follows. Specifically, wires are first formed by the damascene process, that is, a groove is formed in an insulating film and is then filled with a metal film, to mold the metal film by use of the CMP (Chemical Mechanical Planarization) method, thereby forming a plurality of wires. Further, the insulating film located between the wires is removed by etching or the like, to form the air gap. When the air gap is formed as thus described, the top surface thereof is almost as high as the top surface of the wire.